I'd suggest checking any electrical circuit related to the ignition for corrosion. Start at the right handle bar switch pod, looking for dirty/corroded contacts.
Next, remove the fuel tank and inspect all the electrical connectors for corrosion.
Check the older glass tubed fuses carefully as they can look good but have failed internally. Remove them one at a time, making note of what goes where.
The only good way I check these fuses is with a multimeter set on OHMS checking for continuity. The metal end caps can get loose and break the very small filiment ruining the fuse.
Thses are the type AGX not found in some auto parts stores like the more common AGC type is. The AGX is 1" long and the AGC is 1 1/4" long.
The headlight shell will have many main electrical connections in it, including the wiring from the ignition switch, so these need to be inspected.
A very good electrical contact cleaner/preservative I use is called De-oxit made by Caig Labs in San Diego. Their website is
www.deoxit.com
